BWAS 2017: Rockall Trough Part Two - Cetaceans

Blue Whiting Acoustic Survey 2017 Week Two: Saturday 25^th to Friday 31^st March
by Sean O'Callaghan (IWDG Marine Mammal Observer)

The second week of BWAS marine mammal surveys got off to a blank start initially but the following day (Sunday) really signaled the start of a far more productive period.

Survey progress map for 31st March 2017 with thick lines show areas covered (c) Marine Institute

Not long after ascending into the crow’s nest to start the day's effort and while getting myself ready (equipping the necessary gear for the day along with applying some sun cream!) the seabird team began their observations from the bridge deck and spotted the first whales of the day which appeared initially 500m off the starboard bow, lazily surfacing, all the while moving closer to RV Celtic Explorer. Their slanted blows and boxed body shape gave them away as sperm whales and the three of them (one obviously large individual with two smaller individuals, probably juveniles) came within 100m of the vessel before diving under the bow. Moby Dick's relations up-close and personal, a great start to the day! 

Sperm whales (c) Niall T. Keogh

Sperm whales (c) Sean O'Callaghan

Sperm whale dive sequence (c) Sean O'Callaghan

An hour later, two tall blows were picked up out towards the horizon some 2.5km off the bow and when we reached the area both whales passed the vessel, decent views giving them away as fin whales on the move. The most elusive of the Sunday sightings was of an unidentified beaked whale picked up once by Aude through her binoculars while I was on a break. To round the day off we had a few common dolphins make an appearance off the port side showing no interest in the ship which has been the case for most of the survey. We had caught up with the fishing fleet on the northern side of the Porcupine Bank that day and had views of some of the large factory trawlers.

Maartje Theadora (c) Niall T. Keogh

The next batch of activity happened two days later along the shelf edge some 60km west off Mayo where more common dolphins were sighted in the morning while a group of long-finned pilot whales were recorded visually and acoustically simultaneously a kilometre and a half of the port side in the evening (really displaying how both survey methods can complement one another). While trying to get record shots of these pilot whales a distant blow from a large whale was inadvertently captured in their midst’s just as a group of offshore bottlenose dolphins powered past the starboard side to be picked up by those on watch in the bridge along with the seabird team who were up from dinner to see the pilot whales. Unfortunately these dolphins didn’t hang around and continued off in synchronised breaches which were the best that could be captured by the camera. Another day another species for the list!

Offshore bottlenose dolphins (c) Sean O'Callaghan

Wednesday was a day for housekeeping with heavy rain in the morning coupled with poor sea conditions which were unsuitable to watch or safely work in. Thursday was an unexpectedly interesting day, we had moved north into Scottish waters off the Hebrides with a species list standing at six but there was more transects to go yet. The weather had eased off and we were back on effort again. After turning onto a new transect at around 15:00, Aude started to hear a strange sounding whistle on the hydrophone, seemingly getting closer as time passed by. Continuing to watch from the crow's nest with the possibility of a new species in the area it didn’t take long to spot a large, grey, odd-shaped ship lingering on the horizon. We had heard that the survey tracklines might take us past a military exercise later in the day involving submarines, so with the navy-style appearance of the distant ship coupled with the consistency of the whistles being detected on the hydrophone, it became obvious that sonar was being used. About 30 minutes after the first ship was seen, another four appeared on the horizon to the east around the same time as the first marine mammal sighting of the day was made; a group of ten or so common dolphins moving west ahead of us at high speed! The sonar was detected for a further three hours, during which time another lone common was sighted but seemed unphased by the sound (in contrast to the previous sighting). Further sightings of common dolphins, two unidentified large whales and our first Minke whale of the survey capped off the day nicely as we continued north along the shelf edge and over shallow waters. 

Common dolphin (c) Niall T. Keogh

Navy vessels taking part in the 'Operation Joint Warrior' exercise (c) Sean O'Callaghan

Friday proved to be a fruitful day while over the deep Rockall Trough waters near the Anton Dohrn Seamount, with twenty long-finned pilot whales less than 200m off the port side just after conducting a fishing tow and before the day's watch effort began. This group of pilots engaged in some interesting behaviour such as 'spy-hopping'. Later on a lone Atlantic white-sided dolphin was seen to surface twice, giving tantalisingly brief views of the colourful side pattern but just not enough to put it down as a "definite" sighting for that species.

The day ended as the drizzle closed in from the east, with a lone large blow picked up from the crow’s nest some 3km away. Subsequent rain knocked the survey off effort for a while but as soon as it cleared we were met with the sight of a single fin whale lunging in front of the bow almost on cue in perfect sea conditions! It lunged a further three times as we steamed by, making for a nice end to the week despite heavier rain closing in!

Long-finned pilot whales 'logging' at the surface (c) Sean O'Callaghan

Long-finned pilot whale 'spy-hopping'! (c) Sean O'Callaghan

Lunge-feeding fin whale (c) Sean O'Callaghan

Fin whale lunge-feeding sequence (c) Sean O'Callaghan

Our man in the crow's nest... Sean wonders what species is next up for the marine mammal team! (c) Niall T. Keogh

CSHAS Days 5 to 10: Sunny Southeast and the Celtic Deep

Day 5 to 10 sightings: Tuesday 11^th to Sunday 16^th October

We have been playing a game of cat and mouse with some of the largest animals in the ocean over the past week… the whales are currently winning out!

While enjoying excellent weather off Cork during the first few days of the survey, both fin and humpback whales were being seen from headlands in West Waterford (many thanks to Andrew Malcolm for the updates!) but by the time we reached this area the weather had deteriorated to the point such that no large whales were spotted. 

High pressure conditions with easterly winds allow for fantastic visibility and a stunning mix of colours at sunrise and sunset (c) Usna Keating

Similarly, while enjoying the gannet spectacle over the Celtic Deep, our fellow seabird and cetacean surveyors on RV Cefas Endeavour (taking part in the Peltic Survey) encountered up to 12 fin whales on their transect lines just east of us! We saw two Minke whales ourselves that day and as delightful as they are, we were somewhat dismayed to learn that their larger cousins eluded us once again.

The next day, while making our way north along a transect line towards the Saltee islands off Co. Wexford, excellent sea conditions and visibility allowed us to spot two sets of large baleen whale blows several kilometres off which most likely came from fin whales due to the tall and narrow nature of the blows. Another large baleen whale blow was then recorded over the Celtic Deep well to the northwest of Cornwall but the animals body (and thus identity) remained hidden by heavy swell. Slow progress! 

Rainbow over Great Saltee (c) Niall T. Keogh

Common dolphins have thankfully remained abundant, ensuring Meadhbh has been busy racking up the sightings from the crow’s nest. Mostly small groups noted but one sighting of 60+ animals bounding towards the ship with great enthusiasm in rough seas made for quite the sight. A small group of bottlenose dolphins seen on the inshore section of a transect line to the east of Cork Harbour were too distant to get usable dorsal fin pics for photo-ID purposes but it is likely that they are from the 'coastal' group, one of three populations known to occur in Irish waters. We’ve also had a sighting of unidentified dolphins over the Celtic Deep which were most likely bottlenose again.

Common dolphins (c) Niall T. Keogh

Bluefin tuna and Portuguese man o’ war continue to be seen here and there; attempts at capturing breaching tuna on camera are slowly but surely getting better…

Breaching bluefin tuna (c) Niall T. Keogh

A couple of stowaways were also reported to us by the crew! Recently fledged juvenile European storm-petrels out at sea for the first time can become disorientated during rough weather, get attracted to the lights of ships, land on the deck and then find it difficult to get airborne again. Two such birds were found nestled in the corners of the deck and whilst initially looking a little bedraggled and waterlogged, were allowed some time to rest and dry off in our special ‘stormy hotel’ (a box!) before being released safely overboard the following morning. With any luck they will survive and live long and healthy lives (some storm-petrels are known to reach 30 years old!).

Juvenile European storm-petrel (c) Niall T. Keogh

The seabird list for the trip now stands at 25 species after cormorant, grey phalarope, black-headed gull and little gull were added over the past few days. Guillemots and gannets remain by far our most abundant species recorded each day whilst plenty of interest is being added by good numbers of great skuas, yet more yellow-legged gulls (survey tally now at seven birds), occasional sooty shearwaters, puffins, Arctic skuas, small flocks of European storm-petrels, a single Balearic shearwater east of Hook Head and fantastic views of great shearwaters following the ship while some 35 nautical miles northwest of St Ives, Cornwall.

Two grey phalaropes seen just a few miles off Helvick Head (c) Niall T. Keogh

Great shearwaters (c) Niall T. Keogh

Sooty shearwater (c) Niall T. Keogh

Most great skuas seen in the Celtic Sea at this time of year are in the midst of active wing moult (c) Niall T. Keogh

Smaller numbers of pristine juvenile great skuas have also been noted (c) Niall T. Keogh

Adult yellow-legged gull following the ship over the Celtic Deep (c) Niall T. Keogh

1st calendar-year yellow-legged gull (c) Niall T. Keogh

Arrivals of migrant landbirds continued throughout with more meadow pipits, alba wagtails, swallows, redwings and chiffchaffs noted plus additions of skylark, song thrush, starling and even a tiny goldcrest (arguably one of the world’s greatest migrants… a wee bird capable of making almost 1,500km long journeys in just 20 days, across open water and weighing in at just 5 grams!).

Song thrush on RV Celtic Explorer (c) Niall T. Keogh

Chiffchaff on RV Celtic Explorer (c) Niall T. Keogh

WESPAS Days 20 to 25: southern Celtic Sea to northern Bay of Biscay

Day 20 to 25 sightings: 23rd to 29th July 2016

After somewhat of a lull in cetacean activity in the mid Celtic Sea region, things started hotting up (literally!) as we approached the southern reaches of the Irish offshore territory and into UK and French waters. The sea surface temperature peaked at around 18°C and the ocean sunfish were out in force, as were common dolphins, with several groups seen every day ensuring the marine mammal observers were kept busy. We also recorded several breaching tuna, which looked to be bluefin and albacore. Our hoped for leatherback turtles didn't materialise however.

The outermost survey transect lines brought us close to or just over the continental shelf edge, an area of high productivity where several fin whales and even a single striped dolphin were noted. While surveying near the shelf edge along the northern end of the Bay of Biscay one evening, we spotted two very tall blows out towards the horizon line on our starboard side, presumably from fin whales. Soon after, another group of three fin whales crossed the path of the ship ahead of us from port to starboard, offering fantastic views.

Hard to beat good looks at the second largest animal on earth! 

Fin whale (c) William Hunt

 Fin whale (c) William Hunt

Fin whale (c) William Hunt

Fin whale (c) John Power

(you can just about make out the white colour to the right-hand side of the lower jaw in this pic, a diagnostic ID feature for the species)

We had some really nice sightings of bottlenose dolphins too, both near the shelf edge and also over the shallower shelf waters. Each group seemed to give the ship a wide berth, travelling past at distance. We tried to take as many pics as possible to see if we can match them to any known group (bottlenose dolphins with distinctive notches, scars and colourations on their dorsal fins are catalogued across Europe). It would be great to find out which group these animals belong, 'offshore' or 'coastal'?

Bottlenose dolphins (c) William Hunt

Common dolphin (c) William Hunt

Common dolphins (c) Mick Marrinan

Ocean sunfish (c) William Hunt

Sightings of cool marine wildlife have not just been limited to daylight hours. While on transect lines, the ship stops on station at night from midnight to 4am as part of the method for surveying boarfish. During this time a whole manner of life is attracted to the waters around the ship, illuminated by the lights. Fish such as saury start appearing in their droves to feed on gathering plankton which in turn attract predatory species like garfish, blue sharks, common dolphins and even seabirds such as fulmars and European storm-petrels (plus a grey phalarope one night circling the ship, calling!). 

This nocturnal wildlife spectacle has provided the night shift scientists and crew with endless entertainment (the blue sharks stealing the show, hands down). Even some of us day shift observers had to stay up way past our bed time in order to witness it!

Blue sharks (c) John Power

Blue shark (c) John Power

European storm-petrel circling RV Celtic Explorer at 2am (c) Niall T. Keogh

The seabird list finished up on a total of 26 species with the latest additions being Barolo shearwater, grey phalarope and yellow-legged gull. 

Barolo shearwater (which breeds on Atlantic islands such as the Canaries) was a real highlight as it is a rarely observed species around Irish and UK waters but more often seen in the Bay of Biscay, so the bird we saw travelling north with a Manx shearwater just inside the UK offshore territory some 270km southwest of Scilly was perhaps just about on the edge of its perceived regular range, although it seems we have a lot more to learn about their occurrence closer to home as this tracking study has shown.

A flock of 17 grey phalaropes was flushed ahead of the ship on the evening with lots of fin whale activity near the shelf edge along the north side of the Bay of Biscay. These pelagic waders (which feed on zooplankton) will already be on their way south to wintering grounds off the west coast of Africa. On examining pics of the flock, it appeared that quite a few females were present. Grey phalaropes breed in the High Arctic, where the males incubate the eggs and safeguard the chicks during the breeding season while the females leave soon after the eggs have been laid so it is not surprising that we have seen a flock of mostly females this far south already. Their work is done!

A quick check of the gull flock following the ship while west of Brittany yesterday afternoon produced a single fresh juvenile yellow-legged gull, as expected, but enjoyed immensely by the gull enthusiasts on board (...enthusiast, to be precise!).

Otherwise, the past week for the seabird team has been spent soaking up excellent views of yet more Cory's shearwaters and great shearwaters, a very good showing of European storm-petrels and some long-tailed skuas. A few more Wilson's storm-petrels were also seen, bringing the tally for the trip up to 13 individuals. 

Cory's (left) and great (right) shearwaters (c) William Hunt

Cory's shearwater (c) William Hunt

Great shearwater (c) William Hunt

Juvenile lesser black-backed gull (c) Niall T. Keogh

 Gannet (c) William Hunt

Gannets (c) William Hunt

After 25 days at sea, the Western European Shelf Pelagic Acoustic Survey (WESPAS) has come to an end. We are docking in Falmouth in Cornwall this morning from where we will make our way home to Ireland, giving us plenty of time to reflect on the fantastic marine species which we have had the privilege of seeing over the past few weeks. From here the RV Celtic Explorer will make its way to Germany to  undertake another survey.

We'll finish up with a pic of the final species list for the survey and a heartfelt thanks to Chief Scientists Ciaran O'Donnell and Graham Johnston (Marine Institute) for their continued support of offshore marine mammal and seabird surveys and to the officers and crew of RV Celtic Explorer for all their valued assistance throughout the cruise. Until next time...